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Electrochemistry question

2025 · 28 Jan · Shift 2 · Q23
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Electrochemistry question

2025 · 28 Jan · Shift 2 · Q23

JEE MainChemistryElectrochemistryNumerical+4 / −1
Electrolysis of 600 mL aqueous solution of NaCl for 5 min changes the pH of the solution to 12 . The current in Amperes used for the given electrolysis is ‾\underline{\hspace{2cm}}​ . (Nearest integer).
Numerical answer
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Correct answer: 2

  1. Reaction during electrolysis of aqueous NaCl

In aqueous NaCl, at the cathode water is reduced: 2H2O+2e−→H2+2OH−2H_2O + 2e^- \rightarrow H_2 + 2OH^-2H2​O+2e−→H2​+2OH−

Thus, 1 mole of electron produces 1 mole of OH−OH^-OH−.

  1. Use the final pH to find [OH−][OH^-][OH−]

Given final pH = 12, pOH=14−12=2pOH = 14 - 12 = 2pOH=14−12=2 [OH−]=10−2 M[OH^-] = 10^{-2}\,\text{M}[OH−]=10−2M

Volume of solution: V=600 mL=0.6 LV = 600\,\text{mL} = 0.6\,\text{L}V=600mL=0.6L

So moles of OH−OH^-OH− formed are: n(OH−)=[OH−]×V=10−2×0.6=6×10−3 moln(OH^-) = [OH^-] \times V = 10^{-2} \times 0.6 = 6\times 10^{-3}\,\text{mol}n(OH−)=[OH−]×V=10−2×0.6=6×10−3mol

  1. Relate moles of OH−OH^-OH− to charge passed

Since 1 mole e−e^-e− gives 1 mole OH−OH^-OH−, n(e−)=6×10−3 moln(e^-) = 6\times 10^{-3}\,\text{mol}n(e−)=6×10−3mol

Charge passed: Q=nF=6×10−3×96500≈579 CQ = nF = 6\times 10^{-3} \times 96500 \approx 579\,\text{C}Q=nF=6×10−3×96500≈579C

  1. Find current

Time of electrolysis: t=5 min=300 st = 5\,\text{min} = 300\,\text{s}t=5min=300s

Using Q=ItQ = ItQ=It, I=Qt=579300≈1.93 AI = \frac{Q}{t} = \frac{579}{300} \approx 1.93\,\text{A}I=tQ​=300579​≈1.93A

Nearest integer: 2\boxed{2}2​

  1. Comparison with stored answer

Derived answer = 222

Stored correct answer = 222

Hence, the derived answer agrees with the stored correct answer.

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